1. Field of the Invention
The present invention relates to an instrument for measuring a refractive power of an examined eye.
2. Related Art
Conventionally, an instrument for measuring a refractive power has been widely used in various medical fields including departments of opthamology. For example, an instrument utilizing retinoscopy is described in Japanese Unexamined Patent Application Publication No. H06-165757.
The above instrument includes a handheld type that is used for a case where measurement with a stand alone type set on a table is difficult, such as measurements for babies, children, people in wheelchairs, or the like (Japanese Unexamined Patent Application Publication No. H07-213485).
However, when measurements are performed for babies, children, people in wheelchairs, and the like using the handheld type instrument, it is sometimes impossible to acquire sufficient measurement data due to handshaking of an operator and an insufficient time period during which babies and children can keep the eye motionless.
Even if the stand alone type instrument is used, unstable measurement data may be acquired in some cases: when a measurement is performed for a person who has a small pupil, or an abnormal eye position in addition to babies and children, for example. Unstable measurement data may result in problems such as requiring a long time period before obtaining a measurement value and failure to obtain the measurement value.
As a method of performing a refractive power measurement in the above cases, Japanese Unexamined Patent Application Publication No. H08-191795 discloses a method in which an operator operates a switch to change the number of data acquisition.
However, the method of Japanese Unexamined Patent Application Publication No. H08-191795 involves a cumbersome operation of the switch.
Also, the method forces an examinee to have repeated measurements, causing difficulty in measuring the eyes of babies and children.